The present invention pertains generally to interventional medical devices. More particularly, the present invention pertains to catheters that can be used to incise tissue in the vasculature of a patient. The present invention is particularly, but not exclusively, useful as a catheter for incising the aortic valve between the left ventricle of the heart and the aorta for the purpose of relieving the heart condition known as aortic valve stenosis (AS).
In its normal operation, the left ventricle of the heart pumps oxygen-rich blood to arteries in the vasculature of the body through the aorta. As the heart pumps, the aortic valve, which is located between the ventricle and the aorta, opens and closes to control the direction of blood flow. Specifically, during a heartbeat, the valve is open to allow blood to flow from the ventricle into the aorta. Between heartbeats, however, the aortic valve closes to form a tight seal that prevents blood from leaking back into the ventricle. For any of several reasons (e.g. aging, or birth defects), it can happen that the aortic valve is somehow damaged and may become stenosed. When this happens, the aortic valve does not open to its normal extent and the flow of blood from the heart into the aorta is constricted. This leads to a heart condition that is commonly known as aortic valve stenosis (AS).
In a patient with AS, the aortic valve is stenosed and the heart is forced to pump blood through a narrowed opening through the aortic valve. Over time, this narrowing causes pressure to build up in the left ventricle of the heart. In order to compensate for this pressure overload, the muscles of the left ventricle enlarge (hypertrophy) so that the heart can pump with more force. It eventually happens, however, that the stenosis in the aortic valve increases to the point the heart can no longer maintain adequate blood flow through the stenosis. At this point, the patient experiences several characteristic symptoms of AS. In general, this occurs when the aortic valve, when open, has a valve opening area that is approximately one square centimeter (1 cm2).
Heretofore, the treatment for AS has been accomplished either surgically by doing a valve replacement, or by performing a percutaneous balloon valvuloplasty. In the case of a valve replacement, an extensive surgical procedure is required wherein the aortic valve is replaced either by a mechanical or a porcine valve. On the other hand, being a percutaneous procedure, balloon valvuloplasty is somewhat less involved than a valve replacement procedure. Nevertheless, for many reasons including a high recurrence rate, and despite its initial acceptance, balloon valvuloplasty is now used infrequently and only palliatively or as a bridge to surgery.
In light of the above it is an object of the present invention to provide a percutaneous device and method for treating aortic valve stenosis that effectively makes controlled shallow incisions in the leaflets, of the aortic valve to thereby establish a more normal flow of blood from the left ventricle of the heart into the aorta. Another object of the present invention is to provide a cutting device that can be safely advanced through the vasculature of a patient, and subsequently withdrawn therefrom, while permitting surgical incisions at selected locations in the vasculature. Still another object of the present invention is to provide a cutting device and method for treating aortic valve stenosis that is simple to manufacture, easy to use, and comparatively cost effective.
In accordance with the present invention, a cutting device for treating aortic valve stenosis includes a catheter that has an elongated balloon mounted near its distal end. As intended for the present invention, the balloon can be reconfigured on the catheter between an inflated configuration and a deflated configuration. Structurally, the balloon defines an axis and, in its inflated configuration, it has three identifiable sections that are located between its distal end and its proximal end. These sections are: a substantially conical-shaped distal section having a taper with an increasing radius in the proximal direction; a substantially conical-shaped proximal section having a taper with a decreasing radius in the proximal direction; and a substantially cylindrical-shaped intermediate section that is located between the distal section and the proximal section.
At least one, but as many as three or possibly four, substantially straight, elongated blades are attached to the balloon. Importantly, these blades are oriented on the balloon so as to be coplanar with the axis of the balloon. Further, each blade is formed with a sharp edge, and each blade is attached to the balloon to project the sharp edge of the blade in a radial direction from the axis of the balloon. In more detail, the proximal portion of each blade is attached to the proximal section of the balloon, with the distal end of the blade adjacent the distal end of the balloon. The blades, however, are longer than the proximal section of the balloon. Therefore, the distal portion and the distal end of each blade is not attached to the balloon.
In the operation of the present invention, the balloon (in its deflated configuration) is advanced into the vasculature of the patient. Specifically, for the treatment of AS, the balloon is positioned inside the left ventricle of the heart. This then places the balloon distal to the aortic valve. In any event, once the balloon is in the left ventricle it is then inflated.
In its inflated configuration, the balloon inclines each blade relative to the axis of the balloon. Specifically, this inclination is characterized by an increasing distance between the blade and the axis of the balloon, in a distal direction along the axis. In cooperation with the balloon, each blade is inclined relative to the balloon""s axis at an angle (xcex1) that is established by the taper of the balloon""s proximal section, when the balloon is inflated. Preferably, this angle (xcex1) is in a range between approximately zero degrees, when the balloon is in its deflated configuration, and approximately forty-five degrees, when the balloon is in its inflated configuration. (0xc2x0-45xc2x0). An important consequence of this is that, when the balloon is in its inflated configuration, the sharp edges of the blades are presented for cutting (incising) the aortic valve. More specifically, the distal portions and distal ends of respective blades are projected radially outward from the axis through a distance that extends beyond the radius of the cylindrical-shaped intermediate section.
An incising action on the aortic valve is accomplished as the inflated balloon is retracted through the aortic valve in a proximal direction. After the inflated balloon has been retracted through the aortic valve, and the valve has been incised, the balloon is deflated. The deflated balloon is then withdrawn from the vasculature and the procedure is completed.